Hepatitis A virus (HAV) infection is commonly encountered in developing countries. According to the World Health Organization, HAV vaccine should be incorporated into the national vaccination calendar for children aged ≥1 year in countries that are undergoing a transition from intermediate/high endemicity to low endemicity.

HAV antibodies seem to die out over time. Therefore, most hematopoietic stem cell transplantation (HSCT) revaccination guidelines advise vaccination as optional, following the country recommendation. There has been no study to evaluate the serological response to HAV vaccine in allogeneic HSCT recipients.

Adati et al thus carried out a prospective study with 46 HSCT recipients who were given two doses of inactivated HAV vaccine. Blood samples were taken before vaccination to ascertain HAV prevalence rates, and prior to as well as 4-6 weeks after the second dose. Specific anti-HAV antibodies were detected using a competitive commercial enzyme immune assay.

The first dose of vaccine was given at a median of 332.5 (120-4134) days following HSCT. Median absolute lymphocyte count at vaccination was 1947 (696-12 500)/mm³ and the seroprevalence rate at inclusion was 93.5%. Despite being safe and well tolerated, the serological response to HAV vaccine in susceptible patients was found to be poor (33%), with no boost effect seen in seropositive patients. 

To conclude, in areas with intermediate/high seroprevalence of HAV, serology should be recommended before referral to vaccination. There is a need to better understand the mechanisms of antibody interference and the ways to overcome T-cell function deficiency in transplant populations receiving HAV vaccine.

Source: Adati EM, da Silva PM, Sumita LM, et al. Poor Response to Hepatitis A Vaccination in Hematopoietic Stem Cell Transplant Recipients. Transpl Infect Dis. 2020 Jun;22(3):e13258.